New build for myself - Fender Deluxe/Bassman blend

[gui_tarzan]

A friend gave me a non-working Ibanez TSA30 12" combo several years ago. No speaker, but the chassis and cabinet were usable. I just got it working today and I kind of like the way it sounds but still have some tweaking to do. I used the PT and OT that came with it to power a Bassman AB165 (normal channel only) pre-amp & tonestack with one and a half 12AX7s, and the PI and 6V6 power section from a Deluxe. Why? Because I wanted to.

I have to quiet it down though, it's much, much louder than I expected it to be. I'll look at how to do that later, I'm just happy that it's working after struggling with what type of pre-amp to use. Simplicity was the goal with this one and I am glad I did it this way. It was also a learning experience from a theory side too, based on some of the questions I asked about transformers, pre-amp, etc. recently.

The schematic shows the pre-amp and power amp sections put together exactly where I separated them, with a master volume between the two. I'm not really a fan of MVs but if I don't use one here it's far too loud to play in the house. I also didn't put the FB in this yet, I'm going to experiment with different values of parts when I do.

I've needed a "win" for myself lately and I got it with this!

Edit to add: No, I'm not showing a gut shot, it's not customer-quality yet. I have some cleanup to do because it's true point-to-point, no boards inside this one.

[gui_tarzan]

The outside. Nothing special, I just need to figure out how to take advantage of the extra pot holes.

[gui_tarzan]

A 47k resistor on a NFB line quieted it down. I don't care for the tone though, I have some tweaking to do I guess. It sounds harsh when clean, no nice harmonics or that Fender "chime". I may have the bias too cold to start with. I don't remember what it is offhand, I need to check it again but I know it was on the cool side.

[Enzo]

I don't see a NFB on your drawing. You just connected a 47k from speaker to somewhere? COnsider how Fender added NFB on their models.

[gui_tarzan]

I hadn't updated the schem yet. Yes, I did that like their drawings show on the Deluxe Reverb.

[Helmholtz]

Also the power supply chain is not complete. You need at least one more decoupling filter stage.

[catalin gramada]

I hadn't updated the schem yet. Yes, I did that like their drawings show on the Deluxe Reverb.

You cannot put the cathodyne grid to the ground as secondary OT path did. The bias voltage is referenced to elevated voltage by 56k resistor. Move you nfb injection point to the previous stage in cathode.

[Enzo]

Which Deluxe Reverb? Your schematic uses a split load phase inverter, the Deluxe Reverb uses a long tailed pair PI.

[gui_tarzan]

Also the power supply chain is not complete. You need at least one more decoupling filter stage.

I don't have the power supply shown because it's typical Fender with diode rectification. I'll post all the specs when I get it further along.

[gui_tarzan]

You cannot put the cathodyne grid to the ground as secondary OT path did. The bias voltage is referenced to elevated voltage by 56k resistor. Move you nfb injection point to the previous stage in cathode.

I'm not following you. Aside from the NFB I did not modify the power section at all.

[gui_tarzan]

Which Deluxe Reverb? Your schematic uses a split load phase inverter, the Deluxe Reverb uses a long tailed pair PI.

The AA763. It has the LTP and second half of the PI connected to NFB. Again, I'm experimenting with different things. The Traynor YBA1 also uses the LTP and NFB going to the second half. The Bassman AB165 has the LTP with NFB going to the first half of the PI. Obviously there are reasons for each, I will probably change the PI to the LTP based on the results of hooking it up like I did. There seems to be more flexibility with that design.

[Enzo]

But note it does not stick into the grid, it goes down to the bottom of the tail. The NFB comes from the speaker winding, which is a very low DC resistance. SO connecting that to the PI grid will drag it down. The split load is half cathode follower The cathode sits up from ground at substantial voltage. The grid sits at about the same DC voltage as the cathode, except your NFB is in parallel with that to ground. That is what catalin was saying.

[gui_tarzan]

But note it does not stick into the grid, it goes down to the bottom of the tail. The NFB comes from the speaker winding, which is a very low DC resistance. SO connecting that to the PI grid will drag it down. The split load is half cathode follower The cathode sits up from ground at substantial voltage. The grid sits at about the same DC voltage as the cathode, except your NFB is in parallel with that to ground. That is what catalin was saying.

Ok, that makes sense. Thanks for explaining it that way. So that could be exactly why the tone is not right and probably could hurt some components down the road. This is why I love this forum and you guys, as I try different things out of curiosity you bring me back to theoretical and logical center and at the same time I am learning more.

[catalin gramada]

Do this.

[Enzo]

Iit won't damage anything except your tone.